Human Form Innovation

Ergonomic seating is essential in promoting user comfort, health, and productivity in the workplace. This paper examines the scientific principles underpinning the Kinn chair’s design, with a particular focus on its back frame. By incorporating findings from biomechanical research and anthropometric studies, the Kinn chair addresses the diverse needs of users, facilitating better posture and movement throughout the workday.

Varied Sitting Postures: Field studies have shown that individuals assume a wide variety of postures even while performing a single task. Grandjean et al. (1983) and Grieco et al. (1986) observed people working at visual display terminals (VDTs) and noted that they frequently changed positions. Similarly, our research identified three primary modes of sitting at work: forward sitting, slightly reclined sitting, and deeply reclined sitting. Forward sitting, often used for desk work or interacting with office equipment, is common among people of small stature working at fixed-height surfaces (Mandal, 1985). Slightly reclined sitting is preferred for activities such as conversation, telephoning, and keyboarding (Grandjean, 1980; Laubli, 1986). Deeply reclined sitting is typically used for resting, reading, and, occasionally, keyboarding.

Importance of Movement: Experts agree that changing positions while sitting has significant benefits. Muscle movement acts as a pump to improve blood circulation (Schoberth, 1978), while movement of the spine nourishes the intervertebral discs (Holm and Nachemson, 1983). Additionally, reclining pumps nutrients to the discs (Andersson, 1981), and continuous joint movement is therapeutic for joints and ligaments (Reinecke, 1994). However, if a chair requires manual adjustments to shift positions, it may discourage movement, leading to prolonged static postures. Studies have shown that people tend not to use manual adjustments on their chairs (Kleeman and Prunier, 1980; Stewart, 1980).

Anatomical Variations: Variations in spine shape significantly influence how individuals fit into and experience a chair. The spine is divided into four major sections: cervical (neck), thoracic (trunk), lumbar (lower back), and sacral (tailbone). Each section has distinct structural and functional characteristics. The cervical region, consisting of seven vertebrae, is highly flexible and strong. The thoracic region, with 12 vertebrae, has limited mobility due to its connection to the rib cage. The lumbar region includes the five largest vertebrae, capable of significant movement. The sacral region, composed of five fused vertebrae, is held between the pelvic bones.

When properly aligned, the thoracic region exhibits a kyphotic curve (slightly convex), while the cervical and lumbar regions have lordotic curves (slightly concave). These curves create the spine’s characteristic “S” shape. However, individual back shapes vary; some have flat backs, while others have pronounced curvatures. The CAESAR study (2003) highlighted the significant variation in the thoracic region’s height and depth.

Addressing Anthropometric Variations: Anthropometric variations, combined with differences in weight distribution and muscle tension, result in diverse preferred postures. What feels upright or reclined to one person may feel different to another with a different spinal curvature. Traditionally, back support has focused on the lumbar region. Individuals with curved backs benefit from lumbar support that fills the void, preventing lumbar collapse. Conversely, those with flat backs paired with excessive lumbar support may compensate by arching their backs or moving forward on the seat, away from backrest support. These discrepancies require the chair to adapt to the user, rather than the user adapting to the chair.

The challenge is to design a chair that supports the body’s natural equilibrium across upright to reclined postures, facilitating spontaneous movement and comfort in various sitting positions. The chair must provide anatomical support for the extremities and torso, including the four spinal regions, treating them as related but individual entities. Key design objectives include:

The research involved iterative prototyping, extensive user testing, and advanced data collection techniques. Participants from diverse demographics were included to gather comprehensive feedback. Data collection methods included pressure mapping, anatomical analysis, and user surveys.

Three Linked Support Zones: The Kinn chair features three linked support zones: thoracic, pelvic/sacral, and distal thigh. This design ensures that as the sitter shifts from upright to reclined postures, the thigh remains horizontal, the seat pocket stabilizes the pelvis, and thoracic support remains continuous, allowing the sitter to look forward and down without neck strain.

Dynamic Flexibility: To facilitate additional movement in the seated position, the Kinn chair’s tilt mechanism includes an articulation allowing the user to stretch beyond fitted postural support from any tilt-limited position. This extra extension mode, termed the “X-shape” in the back webbing pattern, provides varying support levels at different torso areas. The lumbar region’s wider and more tensioned X-shape maintains good posture, while the thinner, more elastic thoracic section permits unrestricted movement. This approach removes constraints typical of conventional single-part backrests, enabling healthful movement for stretching the neck, shoulders, and lumbar spine.

Advanced Material Integration: The Kinn chair employs 3D sandwich mesh stitched directly onto the elastomer webbing, avoiding traditional fastening methods and preserving edge flexibility. This construction enhances comfort and support by ensuring the backrest adapts dynamically to the user’s movements.

Adjustable Backrest for Individual Needs: The Kinn chair’s backrest can be adjusted to fit individual spinal profiles, promoting postural equilibrium suitable for technology-based tasks. The thoracic support zone can be adjusted forward or rearward through a 25-degree range, allowing users to find their neutral, balanced body posture with the head aligned over the torso and eyes aimed at the horizon. This adjustment accommodates various spinal curvatures, helping users maintain a neutral posture and align naturally with visual displays.

Pressure Mapping and User Feedback: Pressure mapping revealed that the Kinn chair distributes weight evenly across the seat and backrest, reducing pressure points and enhancing comfort. User feedback indicated significant improvements in posture and comfort during extended use.

Enhanced Movement and Flexibility: The Kinn chair’s design promotes natural movement, allowing users to shift seamlessly between postures without manual adjustments. This flexibility is crucial for maintaining spinal health and preventing discomfort associated with static postures.

Sustainability and Durability: The use of advanced, recyclable materials ensures that the Kinn chair is both durable and environmentally friendly. The 3D sandwich mesh and elastomer webbing provide long-lasting support and flexibility, maintaining their structural integrity over time.

The Kinn chair’s innovative design addresses the need for ergonomic seating that supports dynamic movement and postural equilibrium. By incorporating biomechanical principles and addressing anthropometric variations, the chair adapts to individual user needs, enhancing comfort and productivity.

Impact on Workplace Health: The ability to maintain proper alignment and support across various postures reduces the risk of musculoskeletal disorders, a common concern in sedentary work environments. The Kinn chair’s design encourages movement, which is essential for spinal health and overall well-being.

User Adoption and Adjustability: The intuitive design of the Kinn chair minimizes the need for manual adjustments, encouraging users to take full advantage of its ergonomic features. The adjustable backrest ensures that users with different spinal profiles can achieve a comfortable and supportive seating position.